Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$125.90	4.674%	$131.7846	$131.78	$131.80	$131.80
Purchase #2	$237.43	6.538%	$252.9532	$252.95	$252.95	$253.00
Purchase #3	$135.68	5.772%	$143.5114	$143.51	$143.50	$143.50
Purchase #4	$84.52	12.227%	$94.8543	$94.85	$94.85	$94.90
Purchase #5	$152.38	13.461%	$172.8919	$172.89	$172.90	$172.90
Purchase #6	$141.61	7.505%	$152.2378	$152.24	$152.25	$152.20
Purchase #7	$37.57	13.321%	$42.5747	$42.57	$42.55	$42.60
7 purchase totals =	$915.09		$990.8079	$990.79	$990.80	$990.90